Like a ghost rising from the deep, a rare white whale flashed its pale hide off Australia's Gold Coast on Sunday. But despite the inevitable Moby Dick references, this particular animal was a humpback, not a sperm whale.

Since then, two other white humpbacks have been spotted off Australia's coast. One has been dubbed "Migaloo Junior" or the "son of Migaloo"—although no one knows whether this smaller whale is actually related to Migaloo, and a third white humpback with black spots on its tail.

Experts think this most recent sighting may be of Migaloo Junior, not Migaloo, according to theAustralian Associated Press. The animal spotted Sunday is smaller than Migaloo and lacks some distinctive scarring the famous whale received when a boat hit him in 2003.

White whales aren't common, saysJohn Francis, vice president for research, conservation, and exploration at National Geographic, but they aren't unheard of, either.

The marine biologist has encountered white sperm whales off the Azores, and he's heard of white fin or blue whale sightings off the California coast. Francis has also run into white fur seals.

A Rare Condition

White animals can occur throughout nature, he notes.

It stems from genetic mutations, and there are three "versions" or flavors. True albinos are unable to produce any kind of pigment, hence their white coloration and pink eyes: Blood vessels normally masked by eye color show through.

Albinism is a recessive trait, meaning both parents must pass the mutation on to their offspring. Snowflake,an albino lowland gorilla, had parents that passed on copies of a gene found in other albino animals like mice, horses, and chickens.

Leucistic animals are mostly white but can produce some pigment. For example, many still sport color in their eyes.Two white spider monkeys recently spotted in a Colombian rain forest likely have this condition.

A third condition is called "isabellinism," in which a genetic mutation leaches the color out of pigmented penguin feathers. Animals that suffer from isabellinism are different from albino animals because they can still produce pigment. Leucistic and isabelline are sometimes used interchangeably to describe the pale brown or "blonde" coloration of penguins with this condition.